Electronic devices such as laptops, personal data assistants (PDAs), MP3 players, CD players, etc., are very popular. However, these mobile devices often utilize delicate and expensive components, such as magnetic disk drives, that are prone to damage when dropped. Because of the small size and portability of these devices, they are prone to be dropped, particularly as the devices decrease in size. In addition, the devices are often more apt to experience undesirable dynamic (i.e., inertial) loading from drops or falls due to the very fact that they are mobile.
For many reasons, hard disk drives are positioned in sealed, rigid containers or housings. Nevertheless, disk drives used in portable devices are often positioned in a second, larger enclosure before being installed or embedded in the portable device (such as a laptop or MP3 player). The outer enclosure provides additional protection for the disk drive, and also provides space and protection for other electronic components, such as circuit boards, which are utilized in conjunction with a hard disk drives. FIGS. 5A, 5B and 5C illustrate a disk drive housing 12 which, in turn, is positioned in an outer enclosure 14. Shock absorbers 16 are added to decrease the amplitude and generally increase the duration of a shock impulse load and thereby improve survivability of the disk drive. Shock absorbers 16 may be positioned between the housing 12 (FIG. 5A) and an outer enclosure 14, they may be positioned solely on the exterior of the enclosure 14 (FIG. 5B), or both (FIG. 5C).
The objective of a shock absorber used with a disk drive in a mobile product is to reshape the frequency spectrum associated with the energy generated by the shock event in a way that eliminates or reduces damage. Typically, high impact shock events, such as dropping a mobile device containing a disk drive on a hard surface, generate a high amplitude, short duration pulse or shock wave. A shock absorber attempts to decelerate the falling device to reduce the amplitude of the shock pulse by increasing the duration of the shock pulse and/or to dissipate the energy through the deformation of the absorber caused by the resulting impact. Materials having rubber-like characteristics are good shock absorbers because they tend to attenuate high frequency pulses. Energy absorbing materials may be used to dissipate energy as the material is deformed. However, material composition is not the sole factor in selecting a shock absorber. Another factor is thickness or available compression height. Together, material stiffness property, cross-sectional area and available compression height are optimized to achieve the desired frequency spectrum for a given input pulse. To fully or sufficiently absorb a high amplitude shock, the shock absorber must not fully compress or bottom out before the shock pulse is dissipated. Shock absorber thickness or size is a function of the disk drive mass, shock input pulse (amplitude and duration), absorber material properties, and the anticipated shock levels at the worst case shock input pulse scenario. A thick material may be soft. A stiff material may not compress enough. Another factor is space. Where space is a premium, such as in the context of the present invention, the compression height of the shock absorber may be restricted. Optimally, all available space should be considered when designing the characteristics of a shock absorber, including when designing the compression height. A shock absorber also needs space to deform upon deceleration. If its deformation is constrained or hampered, the full potential of the shock absorption characteristics will not be achieved. The greater the available compression or sway space, the more the space can be utilized to optimize the characteristics of the shock absorber.
The prior art methods of FIGS. 5A, B and C have drawbacks. Adding shock absorbers 16 to the exterior of the enclosure 14 (FIG. 5B) increases the size of the enclosure 14 which also increases the size of the overall envelope, i.e., the external dimensions of the electronic device (the laptop computer, MP3 player, etc.). Adding shock absorbers solely between the housing 12 and enclosure 14 (FIG. 5A) or both inside and outside the enclosure 14 can also increase the overall dimensions of the envelope. However, a primary marketing concern for mobile devices is their size. Typically, the larger size of the components, the larger the end product will be. Thus, the larger the external envelope of the disk drive enclosure 14, the larger the entire finished product will be. Moreover, as mobile products decrease in size, the thickness of the outer enclosure 14 tends to increase in order to maintain or enhance protection due to the fact that the smaller form factor affords less protection to the disk drive. An increase in the thickness of enclosure 14 also adds to the increase in overall envelope size. Similarly, as the overall size of the portable device decreases in size, the thickness of the enclosure 14 becomes a larger percentage of the thickness of the overall device. Thus, the shock absorbers are an increasing factor in the overall size of the portable device.
In the environment of a portable consumer electronic product, utilizing shock absorbers solely on the outside of the outer enclosure 14 (FIG. 5B) is unacceptable. Exterior only shock absorbers increase the exterior dimensions of the overall envelope when space is at a premium. Additionally, externally mounted shock absorbers or bumpers do not eliminate the need for internal shock protection located between the disk drive housing and the enclosure due to the compression height and compression travel required of the external shock absorbers to sufficiently dampen a high amplitude shock load. In this regard, external shock absorbers do not fully or optimally use the space occupied by the enclosure 14 for shock absorber compression. In fact, available compression space, i.e., the space 18 inside the enclosure 14 and outside the housing 12 is wasted. Another drawback is that exterior bumpers are typically separate parts that add both component and assembly cost. For example, adhesives are often required to affix the shock absorbers to the external enclosure of the disk drive which increases assembly time and cost.
Positioning shock absorbers 16 only in the space between the disk drive housing 12 and the interior of the enclosure 14 (FIG. 5A) also has drawbacks. Input shocks to the absorber 16 are more severe since the hard outer enclosure 14 experiences the full load of the shock event and passes short duration shocks directly to the shock absorber resulting in high amplitude, short duration pulses that the absorber must dissipate to avoid exciting critical resonances of the disk drive. The enclosure 14 is also more susceptible to cracking or breaking. To avoid damage to the enclosure 14 while providing the same damping as the embodiments of FIGS. 5B and C, the thickness of the enclosure 14 must be increased. To achieve optimal design characteristics, the internal shock absorbers will need to be of a size that either compels an increase in the size of the overall envelope of the enclosure, thus making the entire system larger in size, or the available space and anticipated shock loads used to design the shock absorber will limit any future reduction in size of the envelope.
Similarly, although the embodiment in FIG. 5C advantageously increases the size and volume of the shock absorbers, thereby providing enhanced protection against shocks, it also increases the overall envelope size. However, in the environment of portable electronic devices, unlimited space is not available. Indeed, the design objective is to reduce space requirement, not add to it.
Thus, there is a long felt need in the field of disk drive fabrication to provide a device that protects the disk drive from the harmful effects of physical shock loads while maintaining or decreasing the disk drive's external envelope. Alternatively, there is a need to optimize the use of existing space to increase protection against physical shock loads. The following disclosure describes an improved shock absorber that includes a plurality of protuberances that pass through the outer enclosure to optimize use of space and substantially reduce the effects of high amplitude shock loads.